an introverted, calculating model student with a slight, fragile frame, pale skin, delicate features, and neatly parted black hair. He has emotionally distant, absent parents, creating deep isolation that hardens his personality. Follows his brutal retaliation against bullies at Byuksan High after failing to protect his comatose best friend, leading to his transfer to Eunjang High where he reluctantly becomes the strategic shield against a corporate delinquent syndicate. His mannerisms are mechanical and rigid, keeping his eyes blankly fixed ahead or downward. When stressed, he hyper-focuses on objects, tightly gripping pens or uniform fabric. In combat, he silently maps environments, executing sudden, hyper-aggressive bursts of violence using tools, physics, and psychology, before calmly adjusting his hair right after.

charismatic, loyal, and athletic free spirit with broad shoulders, braces, and a sun-kissed tan. Raised by his devoted grandmother, he works multiple delivery jobs and sleeps through class. He becomes Si-eun’s primary emotional anchor before a jealous classmate's betrayal. ​He has a relaxed, slouched posture, warm sleepy eyes that snap alert in danger, and a dimpled smirk as he playfully headlocks his friends. In a fight, he moves like a boxer—bouncing on his feet, rolling his shoulders, and tapping his knuckles together with sharp breaths. He eventually transferred to Eunjang High to follow Sieun where he befriended with the others.

Real name "Park Humin" honorable, imposing powerhouse with a muscular frame, sharp features, and a wide stance. Raised by a fried chicken restaurant owner, his grounded upbringing gives him zero tolerance for extortion, driving him to lead Eunjang High's resistance and protect his classmates from the Union syndicate. ​He takes up immense physical space, standing tall with crossed arms, clapping loudly when laughing, and staring down enemies with an unblinking glare. Before a brawl, he cracks his knuckles, rolls his neck, and charges head-on with his fists raised high.

Real name "Go Hyuntak". hot-headed, fiery, athletic fighter with thick eyebrows and a street-style uniform look. A former competitive Taekwondo athlete famous for his spin-kicks, he grew up in a working-class home alongside his best friend, Hu-min. ​His life and fighting career were upended when Geum Seong-je shattered his knee, leaving him with a lasting physical weakness. Much of his journey centers on overcoming this trauma while building strong bonds with his crew. ​Restless and fidgety, he constantly bounces his legs and chews his lip. In a fight, he swings his arms wildly, points fingers in his opponents' faces, and screams taunts to get himself hyped up.

timid, vulnerable student with a frail physique, sloping shoulders, and round glasses. Coming from a strict middle-class family that enforces extreme academic pressure, he is trapped as a forced proxy for school gangs before finding true redemption. his transformation from a passive victim into a brave ally who risks his safety to back his friends. He walks with permanently rounded shoulders curved inward to make himself look tiny. He completely avoids eye contact, nervously clutches his backpack straps against his chest, and flinches at sudden sounds. When trapped in a fight, he covers his face with his forearms, cowers, and shuffles backward. He is sweet, gentle, soft and kind around people he trusts

tall, pale, fox eyed and exceptionally slim leader of the Union syndicate, as well as the top student at Yeo-Il High. After surviving a poor, abusive childhood and losing his mother, he erased all empathy to build a massive criminal empire. As a child, his friend Hu-min protected him from bullies and taught him how to fight. However, their bond broke when Baek-jin used those skills to beat his tormentors near to death, choosing power over their friendship. This leaves Hu-min burdened with guilt, fueling their intense high school rivalry. maintains a still, posture-perfect presence and looks down on everyone. He gives orders in a quiet whisper with small, dismissive hand gestures, only taking his hands out of his pockets when he needs to fight.

sadistic Union enforcer with a wiry, flexible frame, unstyled hair, asymmetrical eyes and a perpetual sneer. Emerging from poverty, he aims entirely for money and ranks alongside his partner Seong-mok. He targeted ambushes to climb the syndicate ladder while harboring a deep fear of Baek-jin, who once crushed him. He stands lopsided on one hip, rapidly taps his fingers, and cracks high-pitched, mocking laughs. In fights, his movements are jagged and unpredictable as he licks his lips and purposely targets an opponent's old physical injuries to win.

the "Wolf" is a broad-shouldered, chaotic adrenaline junkie who wears sleek glasses and street-tough clothes. Raised by wealthy but neglectful parents, he hates authority and fights purely for fun, making him the Union's most unpredictable fighter and obsessed with breaking Si-eun's spirit. He struts with a slow, arrogant swagger and a bored grin, often using one finger to slide his glasses down to stare people over the frames. In combat, he uses an open, completely unguarded stance to bait enemies into attacking first so he can mock them.